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I have discovered that my recently installed mini-split is still consuming electric power when it is turned off. This is a 12k btu cooling only TGM mini-split inverter. I noticed that it seemed to be using more electricity than the similar mini-split that it replaced, and I thought that was strange given that both units have the same SEER rating of 21. So I started measuring loads on the circuit with my amprobe. What I discovered is a constant 24/7 load of 0.27 amps on each leg when the unit is off. This is with the remote set to off, air deflection vane in the closed position, no evaporator fan, no condenser fan, and of course no compressor load. I was measuring the load at the breaker and although it is a dedicated circuit, I thought perhaps there might be something else that I don't know about tapping into the circuit. So then I measured the load at the condensing unit and got exactly the same reading - 0.27 amps on each leg with everything off. In my opinion this 24/7 load is not an insignificant parasitic load that would normally be necessary to await a signal from the remote. And by the way, the other mini-split in my apartment is an older single speed unit that draws 0.0 amps when I select the OFF button on the remote. Yet it still responds instantly when I send a signal from the remote to turn on. Any new theories as to what is going on here with my new mini split? I have had this new unit for less than a month, and I am wondering if there is a defect.

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    specifying the exact make/model of the new unit will help. Some may be familiar with it or be able to find the documentation, read it, and find something.
    – FreeMan
    Commented Feb 1, 2021 at 19:09
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    So 65 watts - pretty hefty as parasitic loads go. If it's cooling only, presumably you can shut the breaker off at the end of the cooling season.
    – Ecnerwal
    Commented Feb 1, 2021 at 21:11
  • Well 65VA, actual watts may be substantially lower depending on the power factor. Commented Feb 2, 2021 at 3:20
  • so unplug it when not in use for extended times, rather than use it as a small heater.
    – dandavis
    Commented Feb 2, 2021 at 18:56
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    Is your unit cold-climate rated? If so, that's likely the compressor crankcase (oil) heater burning that power Commented Jun 28, 2022 at 1:23

4 Answers 4

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It's likely a crankcase heater

If the OP's mini-split was designed as a "cold climate" model (or more precisely, its heat pump counterpart in the manufacturer's product line was designed as such), it likely has a crankcase heater on the compressor. This is a small electrical heating element that keeps refrigerant out of the oil when the compressor is not running, thus preventing oil foaming and dilution that starves the system of refrigerant while reducing compressor effectiveness.

One can turn the breaker off when the system is not in use for an extended period of time to remove this load, but one must remember to wait 24-48 hours after turning the breaker back on before calling for cooling from the system if they do this, though, lest the crankcase heater get defeated by dint of being off.

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Your old system did draw current but your measurement equipment was probably not sensitive enough to measure it. If there is a remote to control and activate the system it has to have some power to do this.

Your new system being an inverter based system is also always drawing power the control buss is usually powered up to maintain the charge on the capacitors if it is powered down it will take an average of 30 seconds up to 3 minutes to deplete this charge and to wake the system up takes longer than when in standby and is harder on the electronics.

Where your new system will out preform a single speed system is it can maintain the coolant/ heating levels without starting and stopping all the time but running at a slower rate using less energy overall.

So yes your inverter based system is probably drawing 270ma but this is how that technology works just the elimination of a few hard startups a day will more than compensate for the small draw when not in use. And your equipment was not sensitive enough to measure the 15-20 ma of Curren draw in your old system if the remote can turn it on there is current being consumed.

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    I'd argue that 270mA idle draw is not proper design. At 230V that's 65W; if you leak that through capacitors then you have a huge problem. A control computer for a heat pump should consume <5W, and it's impressive to use 65W. The laptop I'm using to write this uses 65W at full load.
    – vidarlo
    Commented Jul 1, 2021 at 22:22
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    yes. And such a computer should consume hundreds of milliwatts, not tens of watts. 60w standby is just plain bad design
    – vidarlo
    Commented Jul 2, 2021 at 10:20
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    @vidarlo it is more than just a computer, many of the drives consume power just like old TV sets did so they would be instant on. Some Refridgeration equipment turns on a crank case heater when not running this reduces the accumulation of refrigerant in the crank case oil, this could be a majority of the draw, so just thinking with knowledge of the systems may not be helpful.
    – Ed Beal
    Commented Jul 2, 2021 at 17:05
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    And I still would consider that a design fault. 60W is quite a large standby current. I'd happily trade 30 second startup time for this.
    – vidarlo
    Commented Jul 2, 2021 at 17:12
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    @vidarlo in the case of crank case heaters some require 6 hours. Again with no knowledge of how the systems work you are making a lot of assumptions.
    – Ed Beal
    Commented Jul 2, 2021 at 18:14
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I've noted this situation on several mini splits (Senville, Mitsubishi, Fujitsu, Della...) and brought it up to MassCEC - they energy group in my State. Sadly, they couldn't be bothered or concerned as one problem (oil consumption) out weighs the other. I tell my customers to turn off the breaker for the mini split if they will not be using it for an extended period. And I don't think it takes 24 hours to warm the compressor crankcase sufficiently to prevent starting problems. I suggest 1 or 2 hours depending upon outside ambient temperature. The heater is just a resistive element wrapped around the crankcase to keep the oil warm. Some have a resistive heater in the base to insure ice from condensation does not build up but drains.

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As posted above this is simply a function of "stand by" current draw. I can tell you it is common with all mini splits. I have measured the draw on Fujitsu and Cooper Hunter mini splits when in stand by and they both draw close to 0.2A on 240V systems. Depending on your electric rate this draw will amount to between $60 to $130 a year.

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  • @RohitGupta No. You are abusing the "not an answer" flag. This is an answer, although it is probably not correct. The proper remedy for incorrect answers is to downvote.
    – nobody
    Commented Apr 27, 2023 at 23:59
  • @nobody, on reading the question and answer again, you are correct. Commented Apr 28, 2023 at 12:23

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